Tamsulosin can cause males to experience retrograde ejaculation. In males,
retrograde ejaculation occurs when the fluid to be ejaculated, which would
normally exit the body via the urethra, is redirected to the urinary
bladder.

Normally, the sphincter of the bladder contracts and the ejaculate goes to
the urethra, the area of least pressure. In retrograde ejaculation, this
sphincter does not function properly.

Occasionally, tamsulosin can cause a drop in blood pressure, rarely
resulting in dizziness or fainting. Other reported side effects include
headache, dizziness, nasal congestion